The preparation of low density concrete incorporating lightweight hydrophilic aggregates such as vermiculite, cork, slag and the like in a hydrophobic matrix such as a cement mixture are well known. The density and longevity of a cementitious composite are improved through the incorporation of polymeric foam particles, for example, polystyrene foam, as the lightweight aggregate. However, cementitious material, being hydrophilic, has inadequate adhesion to lightweight polymeric aggregates which are hydrophobic while the use of a binding agent in the cement mixture or a pre-coat of the hydrophobic polymeric particles with a binding agent to promote adhesion therebetween has long been contemplated.
The prior art is replete with binding agents including bituminous products, coal tars, mixtures of pitch with polymeric resins, shellac, polyvinyl acetate and the like. Additional additives such as metal ions have been added to binding agents to lessen the tack of the coated particles and lessen coalescence between particles. Prior art lightweight cementitious composites containing hydrophobic polymeric particulate have been limited to certain limitations owing to pumpability problems, cost, environmental concerns regarding binder leachants therefrom, and particle aggregation during mixing and application. Additionally, drying time of prior art composites is sufficiently long that such composites are susceptible to overnight washout before set. Thus, there exists a need for a lightweight cementitious composite material that addresses many of these limitations.